2nd gear slipping/mid gear

[ApullinV6]

Posting for a friend (1kwick6), he just had tranny rebuilt and car shifts really great through all gears at normal and wot passes. The problem is, after car shifts into 2nd gear and car starts pulling hard, tranny starts slipping (almost feels like tires are spinning but are not) Has anyone had this problem or have any ideas what it may be.

Tranny was rebuilt using kevlar clutches and reds ? bands, 10 vein pump and billet adj. servo. were installed.
After Trans. was installed, noticed problem and pulled trans. back out, builder noticed that 2nd gear band had been hot so he replaced band and also replaced servo with a soniox adj. servo. Car is currently doing the same thing since being reinstalled.

Car runs 7.20's in 1/8 mile.

Friend getting frustated, please help?

 

[77 cruiser]

I think he needs to check some pressures.

 

[JDSfastGN]

hook a pressure gauge up for sure. The band being burned before may make this info useless, but i had a similar problem or so i thought. My car would pull through 1st and bang 2nd gear and then would feel like a bad slip. (i know this will sound stupid) I felt like an idiot when i took my dad for a ride and it did nothing. Turns out my factory posi was letting go and it was one wheel peeling with no noise unless i had a passenger which seemed to be just enough to let it hook up (my nittos didn't smoke that i could see.) I really could not feel or hear the one tire letting go but it felt just like how you described. Chances are its the band not holding but i was just throwing this out there.

 

[1kwick6]

update;
i think the pump is/was cavatating, added 1 quart of atf over full mark and problem seems to go away. maybe it is time to get one of those deep
pans and a 700r4 filter.

 

[ApullinV6]

Glad to see you got problem fixed.. and computer ... Well sounds like it's time to go to the strip?